Bacteria: Part II
Classification of Bacteria:
• Bacteria are microscopic prokaryotes.
Prokaryotic cells lack a “true nucleus” that
separates their genes from the cytoplasm.
They lack the various organelles found in
eukaryotic cells
• Eubacteria are prokaryotes that have a
peptidoglycan in their cell walls and lack introns
in their DNA.
• Archaebacteria are prokaryotes that lack
peptidoglycan and have DNA segments similar
to those found in Eukaryotic cells (introns). They
have unusual lipids in their cell membranes.
They can be found in extreme environments--although their is evidence that they may occur in
less severe conditions.
TYPES OF ARCHAEBACTERIA
Methanogens – gain energy by converting H2 &
CO2 into methane gas. They live in anaerobic
conditions, such as the bottom of a swamp and
in sewage, where, they are a source of swamp
gas. They can be found in the intestinal tracts of
humans and other animals, such as cows.
Extreme halophiles –live in environments
of very high salt concentrations such as
the Great Salt Lake and the Dead Sea,
These organisms use salt to generate ATP.
Salt formations
at the Dead Sea
• Thermoacidiphiles – extremely acidic
environments that have extremely high
temperatures, such as hot springs. Some can
thrive at temperatures up to 110o C (230oF) and
at a pH of less than 2. They live near volcanic
vents on land or near hydrothermal vents,
which are cracks
in the ocean
floor miles below the
surface that leak scalding
water
II EUBACTERIA:
1) Phylum Cyanobacteria:
photosynthetic bacteria (example:
Anabaena – live in phosphates in the
water) Some Cyanobacteria can form
heterocysts –specialized cells that can
fix nitrogen for plants. They are
referred to as photoautotrophs.
Anabaena
Nostoc
2) Phylum Spirochetes:
• gram negative, spiral- shaped,
heterotrophic bacteria.
• They move by corksrew rotation.
(Example: Treponema pallidum –
causes syphylis.)
3) Phylum Gram-Positive
Bacteria :
• This group include: yogurt producing
bacteria, streptococci that causes “strep
throat,”& the lactobacilli that cause tooth
decay.
• Actinomycetes – gram-positive,
branching filamentous, soil bacteria.
These bacteria can produce antibiotics.
(examples: erythromycin, tetracycline)
• Included in the group of Gram + are the
endospore-forming bacteria that cause
leprosy, tetanus, tuberculosis and
diptheria.
Tetanus bacteria
• Also: Clostritium botulinum, an
anaerobe, produces a deadly poison
called an exotoxin, that causes death from
botulism food poisoning. (Botox- used in
medical treatment)
4) Phylum Proteobacteria:(Largest and
most diverse group)
• Enteric Bacteria – gram negative bacteria
that inhabit animal intestines E. coli is one
example that can produce Vitamin K for
humans. ----E coli can also cause food
poisoning
• Another enteric bacteria that can cause
food poisoning is the one that causes
Salmonella. Salmonella’s endotoxin is
the cause. It is often found in poultry,
fish and raw eggs.
Chemoautotrophs
• They can extract energy from minerals
(inorganic compounds) by oxidizing the
chemicals within them.
Rhizobium is a nitrogenfixing bacteria that
lives symbiotically
plants in root nodules.
This bacteria is a
major source of
soil nitrogen. (Another is
Azotobacter.)
Bacterial Genetic Recombination:
(more genetic variety)
transformation –
bacteria acquire fragments of DNA from the
environment and incorporate them into their
genome
1. A donor bacterium dies and is degraded.
2. A fragment of DNA from the dead donor
bacterium binds to DNA binding proteins on
the cell wall of a competent, living recipient
bacterium.
3. The Rec A protein promotes genetic exchange
between a fragment of the donor's DNA and
the recipient's DNA.
transduction –
a virus picks up a fragment of DNA from
a donor cell and transports it into the
bacterial cell.
Virus (phage)
particle infects a
bacterial cell
• conjugation – a fragment of DNA (a plasmid
copy) passes from the donor bacteria cell
through a specialized pilus, to a recipient
bacteria cell. The pilus forms a passageway
called a conjugation bridge.
Controlling Bacteria:
1) Antiseptics – chemical used to kill bacteria that
may cause infection such as in wounds. (Used
on people such as iodine, and alcohol)
2) Disinfectant – a chemical solution that
kills bacteria. It is not usually considered a
sterilization method. (Not used on people
– used on surfaces.)
3) Sterilization –(Kills all microbial life)
certain gases, special boiling procedure, &
autoclave – steam under pressure.
ALSO – Radiation, Chemical etc.
autoclave tape
4) Cold temperature – storing food at
refrigeration temperature can slow
bacterial reproduction.
5) High temperature – raising the
temperature of food to destroy bacteria in
cooking, frying etc.
6) Canning – heating food to high
temperatures and then placing in sterilized
glass jars or metal cans and sealing them
properly prevents bacterial growth.
7) Chemically-treating foods – treating
foods with everyday chemicals such as
vinegar, salts and sugar can inhibit
bacteria growth. Salted meats, pickled
vegetables, and jam are examples of
chemically preserved food.
USEFUL BACTERIA:
1) Bacteria are recyclers in the
environment. They can break down
organic matter from dead plants and
animals. They are decomposers.
2) Bacteria are useful in sewage treatment
plants to breakdown sewage into simpler
organic compounds.
3) Bacteria are useful in producing foods
such as: sour cream, yogurt, sourdough
bread, buttermilk, cheese (mozzarella, ricotta,
cheddar …), sauerkraut, soy sauce, &
vinegar.
4) Bacteria produce certain antibiotics.
(Also insulin – genetically engineered bacteria)
5) Bacteria are used in industrial
chemical production .
6) Bacteria have been used in environmental
cleanup. Certain bacteria can also clean up
hazardous chemicals and oil spills in the
environment by converting
the chemicals into other
harmless, or less toxic
compounds. This process
is called bioremediation.
ALSO:
Bacteria present in the microflora prevent
other pathogens from causing an infection.
Additional Uses of Bacteria (pg 476)
• Heat-loving bacteria are a major source of
heat resistant enzymes for biomedicine and
industry. The heat tolerant enzyme Taq
polymerase allows biotechnologists to copy
pieces of DNA rapidly.
• Enzymes from thermophilic
archaea, when added to
laundry detergent, help
dissolve stains.
• Bacillus thuringiensis, (Bt)
makes crystals of proteins
that act as endotoxin for
certain plant pests, such as
the corn earworm caterpillar.
The consumed proteins kill
the insect. (The genes can
be put in the cord directly)
Gut bacteria on different continents